1. Field of the Invention
This invention relates generally to gonioscopes and particularly to a lens suitable for use in performing a goniotomy.
2. Brief Description of the Background Art
A goniotomy is the surgical opening of Schlemm's canal (sinus venosus) by way of the angle of the anterior chamber of the eye. This procedure may be necessary in the treatment of congenital glaucoma. The surgical procedure requires an incision at the limbus which is located at the juncture of a cornea and the sclera. The area within the eye which must be viewed in a goniotomy has to be viewed at an angle of approximately 48.degree. from the horizontal plane including the prone patient. Thus, the surgeon is unable to sit as close to the head of the patient as a surgeon would otherwise prefer. In addition the surgeon must position himself or herself at arms length and stoop down to get into the necessary viewing axis. This causes the surgeon to lose magnification and makes the surgeon unstable for fine surgical procedures.
Because of the need for high precision in the surgical procedure, it would be highly desirable to use a standard opthomologist's operating microscope. However, operating microscopes, designed for a vertical or near vertical, slightly angulated viewing, cannot focus on the eye at the 48.degree. angle required to view the angle through a direct lens. Up to now the procedure is performed with spectacle magnifiers or hand held magnifiers which are cumbersome and give only limited magnification with difficult focusing.
U.S. Pat. No. 4,033,679 to Sussman discloses a gonioscope which is useful for viewing the angle of the anterior chamber. While the design disclosed is suitable for its intended purpose, viewing the angle during a routine examination, it would tend to be awkward if used in a goniotomy. The design would require that the surgeon hold the lens on the eye and simultaneously perform the operation which would not be feasible. In addition the design would not be useful with a operating microscope using coaxial light.
U.S. Pat. Nos. 4,134,647, 4,378,147 and 3,820,879 all disclose various lenses useful in conjunction with the treatment of the human eye. However, these lenses are not adapted for use in conjunction with goniotomies.